What does "Water Activity" refer to in a food product?

Water activity refers specifically to the quantity of free water present in a food product. This free water is the portion of the total moisture that is not bound to the food matrix and is available for microbial growth, chemical reactions, and enzymatic activity.

In the context of food science, free water is crucial because it influences the texture, stability, and quality of food products. For example, in confections and chocolate, controlling water activity is essential to prevent spoilage and maintain product integrity.

The other choices describe different aspects of water within food. Bound water relates to water that is tightly held by food molecules and is not available for reactions, while total moisture content refers to both bound and free water combined. Density, although related to the physical properties of a food, does not specifically address water content or activity. Thus, the focus on free water in option C makes it the correct description of water activity in food products.